The present invention relates to retroreflective interrogation response systems and, more particularly, to a system utilizing a specialized radio frequency tag configured to enhance the identification of a signal reflected therefrom.
A variety of retrodirective interrogation response systems have been proposed for use in systems for remote detection, location, identification, and monitoring of physical objects including persons and vehicles. Typical systems include a radio frequency (RF) responder, such as a remote tag device, and an interrogator. The remote tag device may be arranged to accept a signal, uniquely encode the signal, and retransmit the encoded signal back to an interrogator.
For example, U.S. Pat. No. 5,254,997, issued to Cohn, teaches a retrodirective interrogation responsive system wherein a responder, illuminated by an interrogator, receives an interrogation signal, modulates information onto the interrogation signal, and retransmits the encoded interrogation signal back in the direction of arrival of the collected interrogation signal. The responder uses a Van Atta array antenna and is capable of responding to an interrogator signal incident over a wide solid angle of arrival while retrodirectively retransmitting without amplification substantially all of the collected signal within a narrow solid angle. The device is capable of accepting a signal, uniquely encoding the signal and retransmitting the encoded signal back to the interrogator.
Although there are a number of advantages associated with the system proposed by Cohn and the other conventional systems noted above, the present inventors have recognized that there is a continuing need for an identification system that provides for further enhancements in the manner in which tags or transponders are constructed and utilized to detect and identify an object with which the tag is associated.